1. Field of the Invention
The present invention is directed generally to a method for observing a scene including portraying on an image portrayal side an image of the scene acquired with a wide field of view as well as an image of the scene acquired with a narrow field of view, and to an apparatus for implementing the method including an image system having two optical channels with different fields of view on the image pick-up side. The invention is particularly applicable to infrared imaging systems (FLIR).
2. Description of the Related Art
Thermal imaging apparatus are currently frequently used for observing a scene. Although thermal image apparatus may be used during the day, such apparatus are also used at night for locating and observing thermal radiating objects and, in combination with suitable portrayal devices, also is used for flying aid and navigation at night. For observation of a large region in general and particularly for flying aid and navigation at night, it is particularly desirable to be able to both survey the entire scene as well as to recognize details within the overall scene. It is, therefore, expedient to observe the scene with two thermal imaging devices having different magnifications to thereby observe the scene with a first thermal imager and reproduce it at a 1:1 scale, and at direct a second thermal imaging device to an object to be recognized and then switch to a magnified image of the scene. Such methods, however, have the disadvantage that the observer has only the picture of the overall scene or only a detailed picture available.
A method wherein an observer is offered both the image of the overall scene as well as a detailed, or magnified, image is disclosed in German Patent 31 46 552. The disclosed method provides at least two pick-up systems for images that have different imaging scales. Also disclosed is a corresponding plurality of monitors allocated to the respective pick-up systems, whereby a frame symbol whose bounded picture detail corresponds to the magnified image of a first monitor is mixed into the overall image of a second monitor, for example, and whereby the variable frame symbol automatically follows the relative motion of the pick-up systems in height and laterally. An image of the overall scene and a detailed, or magnified, image is thus offered to the observer simultaneously on a plurality of monitors corresponding to the plurality of pick-up systems, i.e. on at least two monitors. The frame symbol mixed into the second monitor makes it possible to recognize what detail the first pick-up system is directed to and where the detailed image of the first monitor lies in the overall scene. The frame symbol that is mixed in is adjusted based on the relative movement of the two pick-up systems relative to one another, the pick-up systems being pivotable relative to one another.
At the image portrayal side, however, the known method requires at least two monitors so, for one person operation, the observer must simultaneously direct her attention to two monitors or must switch her line of sight from one monitor to the other when observing a larger area and when observing and recognizing details within the overall scene. Such a method is therefore not well suited for a one person operation. Moreover, the transmission properties of the apparatus chain up to the eye only allow a limited recognition of details at limited range.